The court will decide what evidence will be admitted at the time of the trial (no earlier than trial).
Between now and trial, the parties normally exchange discovery requests and take depositions in order to gather and ascertain what evidence exists.
In most courts, the parties must exchange witness lists, exhibit lists and exhibits prior to the Final Status Conference (or Trial Readiness Conference). Your court's Case Management Order may indicate what is required, or if not, the Local Rules of the court may provide guidance.
Frank W. Chen has been licensed to practice law in California since 1988. The information presented here is general in nature and is not intended, nor should be construed, as legal advice for a particular case. This Avvo.com posting does not create any attorney-client relationship with the author. For specific advice about your particular situation, please consult with your own attorney.
It all happens at trial.
Please understand that your question is "what happens in a lawsuit after a complaint and answer?" No one wants to be unhelpful, but the answer is "everything". If affordable, please consider hiring an attorney, even for a few hours when really, really needed. If not, try to see a civil trial to see your questions answered in practice.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.